面向6G的空间可重构天线系统：基于电磁的信道建模、测量与方向设计
Spatially Reconfigurable Antenna Systems for 6G: EM-based Channel Modeling, Measurements, and Orientation Design
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中文总结 AI 辅助
本文针对6G SRASs现有信道模型忽略电磁矢量特性的问题，提出基于球矢量波展开的电磁信道模型，结合流形优化方法优化天线方向，可将多用户MIMO系统总速率提升16.6%至19.3%。
中文摘要 AI 辅助
空间可重构天线系统（SRASs）被公认为第六代（6G）系统的关键物理层技术。通过动态调整每个天线单元的空间配置，如位置和方向，SRASs可重构有利的信道条件以实现可靠的高速数据传输。然而，在广泛采用的信道模型中，天线通常被建模为理想的各向同性辐射器，且电磁（EM）传播的矢量特性被忽略。这种过度简化的模型阻碍了对SRASs所提供的自由度的充分利用以提升性能。为解决该问题，本文利用球矢量波展开的理论框架，开发了一种适用于SRAS支持的多输入多输出（MIMO）系统的基于电磁的信道模型。所提出的基于电磁的信道模型适用于任意结构的天线，且固有地考虑了电磁传播的矢量特性，从而能够准确表征诸如极化失配对信道增益的电磁效应。本文开展了全波模拟和实验测量，结果显示与理论预测高度吻合。模拟结果还表明，天线方向相较于天线位移对可达速率的影响更为显著。因此，基于推导的信道模型，本文提出了一种流形优化方法，通过优化天线方向来最大化SRAS支持的多用户MIMO系统的总速率。模拟结果表明，与采用可移动天线和传统固定天线的系统相比，所提出的方案分别将总速率提升了高达16.6%和19.3%。
英文摘要
Spatially reconfigurable antenna systems (SRASs) are recognized as a key physical-layer technology for sixth-generation (6G) systems. By dynamically adjusting each antenna element's spatial configuration, e.g., position and orientation, SRASs can revamp favorable channel conditions for reliable high-rate data transmission. However, in widely adopted channel models, antennas are typically modeled as ideal isotropic radiators, and the vectorial nature of electromagnetic (EM) propagation is neglected. This oversimplified model precludes full exploitation of the degrees of freedom offered by SRASs for performance enhancement. To address this issue, in this paper, by leveraging the theoretical framework of spherical vector wave expansion, we develop an EM-based channel model tailored for SRAS-enabled multiple-input multiple-output (MIMO) systems. The proposed EM-based channel model is applicable to antennas with arbitrary structures and intrinsically accounts for the vectorial nature of EM propagation, thereby enabling accurate characterization of EM effects such as polarization mismatch on channel gain. Full-wave simulations and experimental measurements are conducted, and the results show excellent agreement with theoretical predictions. Simulation results also reveal that antenna orientation exerts a more pronounced influence on the achievable rate than antenna displacement. Therefore, building upon the derived channel model, a manifold optimization method is proposed to maximize the sum-rate of an SRAS-enabled multiuser-MIMO system by optimizing antenna orientations. Simulation results demonstrate that the proposed scheme improves the sum-rate by up to 16.6\% and 19.3\% compared to systems employing movable antennas and conventional fixed antennas, respectively.
